浅拷贝 &&深拷贝

B对象复制了A对象，当修改A对象时，看B对象是否会发生变化，如果B对象也跟着变了，说明这是浅拷贝。，如果B对象没变，那就是深拷贝。

浅拷贝

1. 普通函数

function shallowClone (source){
     if(!source || typeof source != 'object'){
         throw new Error ('error');
     }
     let targetObj = source.constructor === Array ? [] : {};
     for(let keys in source) {
         if(source.hasOwnProperty(keys)){
             targetObj[keys] = source[keys];
         }
     }
     return targetObj
}
let obj ={
    name:"zhang",
    age:16,
    sex:"men",
    friends:["wang","zhang","li"]
}
let obj2 = shallowClone(obj)
obj2.friends.push("tan")
console.log(obj2) //{name: "zhang", age: 16, sex: "men", friends: ["wang", "zhang", "li", "tan"]}
console.log(obj)  //{name: "zhang", age: 16, sex: "men", friends: ["wang", "zhang", "li", "tan"]}

2. 使用ES6的Object.assign浅拷贝

let obj ={
    name:"zhang",
    age:16,
    sex:"men",
    friends:["wang","zhang","li"]
}
let obj2 = Object.assign({}, obj);
obj2.friends.push("tan")
console.log(obj)
console.log(obj2)

深拷贝

let obj1 = {
         arr: [1, 2, 3],
         obj: {
             key: 'value'
         },
         func:function(){
             return 1;
         }
    };
    let tar={}
    function copy(selfObj,targetObj ={}){
        for (let name in selfObj){
            if(typeof selfObj[name] === "object"){  // 判断对象下的属性是对象（数组）还是普通value
                targetObj[name] = (selfObj[name].constructor == Array) ? []:{};// 判断是数组还是对象
                copy(selfObj[name],targetObj[name]); // 递归调用克隆对象下的对象
            }else{
                targetObj[name] = selfObj[name] // 如果不是对象，直接把值赋给目标对象。
            }

        }
        return targetObj
    }
    obj2 = copy(obj1)
    console.log(obj2 == obj1)